Added comment about current implementation limitations and stored the computed value in the static data holder for future use as it is computed on the fly.
For visibility reasons:

FibonacciChildComputerWithDataHolder becomes inner class of FibonacciComputerWithDataHolder.
FibonacciDataHolder becomes static inner class of FibonacciComputerWithDataHolder.
Final fixes and log messages on screen for debugging purposes.
Refactoring
FibonacciComputerWithReadWriteLockDataHolder implementation attempted but it proves that an implementation with locks is not possible since the current thread that would hold the lock depends and would need to be unlocked by the "child" threads which computed some data for the "parent" thread.

Next try: CyclicBarrier for synchronization.
Compute Fibonacci with CycleBarrier synchronization.